Input: serio_raw - shut up errorneous warning

drivers/input/serio/serio_raw.c: In function 'serio_raw_read':
drivers/input/serio/serio_raw.c:163: warning: 'c' may be used uninitialized in this function

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>